The base notification layout has not changed, so app notifications designed for versions earlier than Jelly Bean still look and work the same. Check the updated Notifications page for more details.

Resizable Application Widgets

Widgets are an essential aspect of home screen customization, allowing "at-a-glance" views of an app's most important data and functionality right from the user's home screen. Android 4.1 introduces improved App Widgets that can automatically resize and load different content based upon a number of factors including:

Where the user drops them on the home screen

The size to which the user expands them

The amount of room available on the home screen

You can supply separate landscape and portrait layouts for your widgets, which the system inflates as appropriate when the screen orientation changes. The Application Widgets has useful details about widget types, limitations, and design considerations.

Accessibility

One of Android's missions is to organize the world's information and make it universally accessible and useful. Our mission applies to all users-including people with disabilities such as visual impairment, color deficiency, hearing loss, and limited dexterity.

The new Accessibility page provides details on how to design your app to be as accessible as possible by:

Making navigation intuitive

Using recommended touch target sizes

Labeling visual UI elements meaningfully

Providing alternatives to affordances that time out

Using standard framework controls or enable TalkBack for custom controls

Trying it out yourself

You can supply separate landscape and portrait layouts for your widgets, which the system inflates as appropriate when the screen orientation changes. The Widgets page has useful details about widget types, limitations, and design considerations.

Ice Cream Sandwich - Android 4.0

Navigation bar

Android 4.0 removes the need for traditional hardware keys on phones by replacing them with a
virtual navigation bar that houses the Back, Home and Recents buttons. Read the Compatibility pattern to learn how the OS adapts to phones with hardware buttons and how pre-Android 3.0 apps that rely on menu keys are supported.

Action bar

The action bar is the most important structural element of an Android app. It provides consistent navigation across the platform and allows your app to surface actions.

Multi-pane layouts

Creating apps that scale well across different form factors and screen sizes is important in the Android world. Multi-pane layouts allow you to combine different activities that show separately on smaller devices into richer compound views for tablets.

Selection

The long press gesture which was traditionally used to show contextual actions for objects is now used for data selection. When selecting data, contextual action bars allow you to surface actions.